Networking CAN nodes together

[dkfire]

We use the same setup as Sam is describing, in every details.

In office and on most setup, we use the NI-USB 8473, but for some cases we use the 9268 as a module in cDAQ chassis.

I would recommend you to start learning CAN, it does not seems to me that you know anything about CAN or how CAN works.

There should be some information on the Internet, for you to learn CAN.

When you have learned CAN you know why there are some different options on CAN cards.

For the LIN option, LIN is another bus technology.

For Low/High option, it all depends on the speed that your CAN network is running. Low speed option only go up to a baudrate of 125kbps. High option can go up to 1Mbps.

If you have a cDAQ chassis with a slot open, then use the NI 9268 module.

The NI 9268 is just the c module.

The NI USB-9268 is a c module with a one slot chassis, that gives the price difference. (The one slot chassis can be used with many different C modules)

Regarding the XNET and NI-CAN, then it is "just" different drivers. With different drivers for different CAN modules you get different options/features. 

NI-CAN driver was the first driver that NI had for its CAN hardware. As the hardware has evolved, the features it can do has increased, so the drivers need to be updated/extended.

And for the Breakout box, don't buy that.

Hope this helps.

[David-Baratheon]

I am looking at the high speed and low speed modules and it really isn't clear to me what the purpose of the low speed one is:

https://www.ni.com/en-us/support/model.ni-9861.html

https://www.ni.com/en-us/shop/model/ni-9862.html

Since on both spec the minimum speed is 40kB/s, but the high speed has a far higher maximum speed, whats the point of the low speed module? Its the same price. I can't realluy see why anyone would ever buy it.

My sensor is 55kB/s so it should in theory work with both modules but since I may use it again in future then I cant see why I wouldnt just get the high speed one in case I need it for faster data transfer.

[nathand]

Here's a brief explanation of the difference between high speed and low speed CAN:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019LzHSAU&l=en-US

[David-Baratheon]

Ah ok so basically they are two different standards for the physical layer. So which one I choose will determine voltage levels and other characteristics and not  just baud rate. if I am understanding correctly. So my sensor should have defined which standard it will use for the physical layer basically? The data sheet doesnt even feature the word high speed or low speed in the entire datasheet.

[David-Baratheon]

It  does mention that CANopen uses High speed so perhaps this is a given. I guess I will just go for high speed then.

That link is super useful and interesting btw

[PeterFoerster]

Good that you're reading up on the topic, but how did we get from CAN to CANopen?

[David-Baratheon]

I have a compact RIO chassis (9022) and a CAN open module (9881) and I need it to communicate with two motors and two sensors, each of which communicates in CANopen. So I needed to network 4 devices together. Since the CAN open protocol runs ontop of a CAN network then I was looking to create a CAN network in hardware and then run my CAN open communications on it. Wasn't sure whether to purchase a breakout box for £300+ or if I could implement it myself with a few cables and resistors. Its just a prototype so doesn't need to be anything fancy, as long as its connected properly so that it has the resistance, power etc required for it to work.

[David-Baratheon]

I would like to start with just getting comms between one sensor and the Compact RIO to ensure communications is working and see if I can get the correct sensor data before I move on to building a CAN network.

Given that the sensor has 4 terminals I need for CAN, can I run those 4 terminals with wires going into a female 9 pin D-sub and pplug that into my module? Where do I put these resistors and power rails?

[nathand]

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@David-Baratheon wrote:

Given that the sensor has 4 terminals I need for CAN, can I run those 4 terminals with wires going into a female 9 pin D-sub and pplug that into my module? Where do I put these resistors and power rails?

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Did you look at the NI 9881 Getting Started Guide? It has a diagram showing how to connect the device and where to put the terminating resistors.